Question

State whether each of the following increases or decrease across a period and down a group.

1. Ionization enthalpy

2. Electron gain Enthalpy

3. Electronic Affinity

4. Lattice Enthalpy

5. Electronegativity

6. Electro positivity

Answer 1

1. Moving left to right within a period or upward within a group, the first ionization energygenerally increases. As the atomic radius decreases, it becomes harder to remove an electron that is closer to a more positively charged nucleus.
2. In a period size decreases from left to right and hence electrons are more tightly held to the nucleus. so electron gain enthalpy increases across a period .down the period size increases and thus in general electron gain enthalpy decreses
3. Electron affinitygenerally increases across a period in the periodic table and sometimes decreases down a group.
4. As atomic radius increases, i.e when you go down a column, lattice energy decreases. Lattice energy increases with the charge on the ions forming the lattice, so for elements that regularly form bonds with 2+ ions, theirlattice energy is still going to be greater than that of a smaller atom with a smaller charge.
5. as you move down a group on the periodic table, the electronegativity of an element decreases because the increased number of energy levels puts the outer electrons very far away from the pull of the nucleus. Electronegativity increases as you move from left to right across a periodon the periodic table.
6. electropositivity is the opposite of electronegativity. As the size of atom increases,its nuclear charge decreases and its tendency to donate electrons increases and therefore electropositivity increases down thegroup while it decreases across a period.